1. Field
This invention relates to an apparatus for measuring properties, such as temperature and humidity, of gases being supplied to a patient. Humidifiers are commonly controlled by measuring the temperature of gas at two points, adjacent to the output of the humidifier and proximal to the patient. This invention predominantly relates to the measurement of temperature of gas supplied to a patient at a point proximal to the patient.
2. Description of the Related Art
The gases temperature supplied to a patient when the patient is undergoing treatment such as oxygen therapy or positive pressure treatment for conditions such as Obstructive Sleep Apnea (OSA) or Chronic Obstructive Pulmonary Disease (COPD) is often measured for safety and to enable controlling of the humidity delivered to the patient. Measurement of temperature near the patient is commonly performed using a probe inserted into the breathing tube, such as that of Fisher & Paykel Healthcare Limited, U.S. Pat. Nos. 6,272,933 and 6,584,972. Such a temperature probe is connected to the humidifier through a cable that runs external to the breathing circuit This approach has some drawbacks. In particular, the user must correctly install the temperature probe. If the probe is not correctly installed then the humidification system may malfunction which may increase risk to the patient. Existing end of breathing tube sensors require sensor wires to be run down the outside of the breathing tube. This lowers reliability of the sensors due to the vulnerability of these wires. Alternatively, if these wires are run down the inside of the breathing tube there would be an increase of the resistance to airflow and the hygiene of the breathing circuit would be lowered.